* @param domain
     *            domain for NTLM fallback
     * @param username
     *            user for NTLM fallback
     * @param password
     *            password for NTLM fallback
     */
    public Kerb5Authenticator ( Subject subject, String domain, String username, String password ) {
        super(domain, username, password);
        this.canFallback = true;
        this.subject = subject;
    }